Predators Help Restore Biodiversity in Yellowstone: In the past dozen years, Yellowstone National Park has been the site of a grand experiment in managing biodiversity. The park is renowned for its wildlife and wilderness. But between about 1930 and 1990, park managers and ecologists observed that growing elk populations were overbrowsing willow and aspen. Plant health and diversity were declining, and populations of smaller mammals, such as beaver, were gradually dwindling. Most ecologists blamed these changes on the eradication of one of the region’s main predators, the gray wolf ( Canis lupus). Now, a project to restore wolves has provided a rare opportunity to watch environmental change unfold.

Figure 5.3 Biomes most likely to occur in the absence of human disturbance or other disruptions, according to average annual temperature and precipitation. Note: This diagram does not consider soil type, topography, wind speed, or other important environmental factors. Still, it is a useful general guideline for biome location.

Estuaries are bays where rivers empty into the sea, mixing fresh water with salt water. Salt marshes, shallow wetlands flooded regularly or occasionally with seawater, occur on shallow coastlines, including estuaries

By focusing on populations already reduced to only a few individuals, we spend most of our conservation funds on species that may be genetically doomed no matter what we do.

It is time to focus on a rational, continent-wide preservation of ecosystems that supports maximum biological diversity rather than a species-by-species battle for the rarest or most popular organisms.